1. Field of the Invention
This invention relates to an upright vacuum cleaner and, more specifically, to an upright vacuum cleaner having indicators which display full filter bag and clogged filter conditions thereof.
2. Description of the Related Art
Upright vacuum cleaners comprise a floor-engaging nozzle having a pivotally-mounted handle thereon which can be driven by a user in an oscillating fashion over a floor surface to be cleaned. The nozzle typically has a suction opening having a rotating agitator brush driven by a motor. The motor also suctions debris loosened from the floor surface by the agitator brush through a suction passage in the nozzle. The suction passage has an inner end fluidly interconnected with a suction passage in the handle which terminates in a filter bag located within the handle.
Upright vacuum cleaners are typically classified as "clean-air" and "dirty-air" systems. Clean-air systems have the vacuum motor positioned downstream of the filter bag whereby suction applied by the vacuum motor to the filter bag pulls air through the suction passages in the nozzle and handle. Dirty-air systems have the vacuum motor positioned upstream of the filter bag whereby debris pulled into the suction passage in the nozzle is "blown" into the suction passage in the handle and, in turn, into the filter bag located therein. In either case, exhaust from the vacuum motor is typically dispensed from either the nozzle or the handle through louvered vents in the housing for the motor.
As debris accumulates within the filter bag, the vacuum motor is required to exert additional pressure on the filter bag in order to accumulate the debris loosened by the agitator brush therein. When a sufficient amount of debris has accumulated within the filter bag, a user must open the housing in which the filter bag is stored and replace it. Because the efficiency by which the vacuum cleaner removes debris from the floor surface is often difficult to ascertain by a user, it is desirable to provide the vacuum cleaner with an indicator which displays a clogged condition of the filter bag. Prior art filter bag indicators for a vacuum cleaner are shown by example in U.S. Pat. Nos. 4,733,430 (Westergren) issued Mar. 29, 1988, 4,733,431 (Martin) issued Mar. 29, 1988, 3,936,904 (Bashark) issued Feb. 10, 1976 and 5,201,095 (Choi) issued Apr. 13, 1993.
However, the filter bags located within the vacuum cleaner typically have a predetermined porosity. Thus, debris particles smaller than the porosity of the filter bag are allowed to pass through the filter bag and out of the vents in the motor housing, returning the debris to the room from which it was removed. To reduce the number of particles entrained within the air exiting therefrom, vacuum cleaners are typically provided with a filter element located downstream of the filter bag either between the filter bag and the vacuum motor or downstream of the vacuum motor, such as in an exhaust air stream thereof. The Westergren '430 patent discloses the use of such a filter element to capture particles escaping the filter bag.
Unfortunately, these filter elements become clogged when a sufficient number of particles are trapped thereon which also reduces the cleaning efficiency of the vacuum cleaner. A user may mistakenly replace the filter bag instead of a clogged filter element when the user determines that the cleaning efficiency of the vacuum cleaner is reduced. Although replacement of a clogged filter bag causes a substantial increase in the effectiveness of the vacuum cleaner, an optimum level of performance is not reached if the downstream filter element is also clogged. Further, it is difficult for a user to ascertain the condition of the filter element and to determine whether either, or both, of the filter bag and filter element have become clogged.